/*
 * Copyright (c) 2025, Jelle Raaijmakers <jelle@ladybird.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/Time.h>
#include <LibWeb/Bindings/GeolocationPrototype.h>
#include <LibWeb/Bindings/Intrinsics.h>
#include <LibWeb/DOM/Document.h>
#include <LibWeb/DOM/DocumentObserver.h>
#include <LibWeb/Geolocation/Geolocation.h>
#include <LibWeb/Geolocation/GeolocationPosition.h>
#include <LibWeb/HTML/EventLoop/Task.h>
#include <LibWeb/HTML/Scripting/Environments.h>
#include <LibWeb/HTML/TraversableNavigable.h>
#include <LibWeb/HTML/Window.h>
#include <LibWeb/Platform/EventLoopPlugin.h>
#include <LibWeb/Platform/Timer.h>
#include <LibWeb/WebIDL/AbstractOperations.h>

namespace Web::Geolocation {

static constexpr u32 VISIBILITY_STATE_TIMEOUT_MS = 5'000;

static WebIDL::UnsignedLong s_next_watch_id = 0;

GC_DEFINE_ALLOCATOR(Geolocation);

Geolocation::Geolocation(JS::Realm& realm)
    : PlatformObject(realm)
{
}

void Geolocation::initialize(JS::Realm& realm)
{
    WEB_SET_PROTOTYPE_FOR_INTERFACE(Geolocation);
    Base::initialize(realm);
}

void Geolocation::visit_edges(Visitor& visitor)
{
    Base::visit_edges(visitor);
    visitor.visit(m_cached_position);
    visitor.visit(m_timeout_timers);
}

// https://w3c.github.io/geolocation/#dom-geolocation-getcurrentposition
void Geolocation::get_current_position(GC::Ref<WebIDL::CallbackType> success_callback,
    GC::Ptr<WebIDL::CallbackType> error_callback, PositionOptions options)
{
    // 1. If this's relevant global object's associated Document is not fully active:
    auto& window = as<HTML::Window>(HTML::relevant_global_object(*this));
    if (!window.associated_document().is_fully_active()) {
        // 1. Call back with error errorCallback and POSITION_UNAVAILABLE.
        call_back_with_error(error_callback, GeolocationPositionError::ErrorCode::PositionUnavailable);

        // 2. Terminate this algorithm.
        return;
    }

    // 2. Request a position passing this, successCallback, errorCallback, and options.
    request_a_position(success_callback, error_callback, options);
}

// https://w3c.github.io/geolocation/#watchposition-method
WebIDL::Long Geolocation::watch_position(GC::Ref<WebIDL::CallbackType> success_callback,
    GC::Ptr<WebIDL::CallbackType> error_callback, PositionOptions options)
{
    // 1. If this's relevant global object's associated Document is not fully active:
    auto& window = as<HTML::Window>(HTML::relevant_global_object(*this));
    if (!window.associated_document().is_fully_active()) {
        // 1. Call back with error passing errorCallback and POSITION_UNAVAILABLE.
        call_back_with_error(error_callback, GeolocationPositionError::ErrorCode::PositionUnavailable);

        // 2. Return 0.
        return 0;
    }

    // 2. Let watchId be an implementation-defined unsigned long that is greater than zero.
    auto watch_id = ++s_next_watch_id;

    // 3. Append watchId to this's [[watchIDs]].
    m_watch_ids.set(watch_id);

    // 4. Request a position passing this, successCallback, errorCallback, options, and watchId.
    request_a_position(success_callback, error_callback, options, watch_id);

    // 5. Return watchId.
    return watch_id;
}

// https://w3c.github.io/geolocation/#clearwatch-method
void Geolocation::clear_watch(WebIDL::Long watch_id)
{
    // 1. Remove watchId from this's [[watchIDs]].
    m_watch_ids.remove(watch_id);
}

// https://w3c.github.io/geolocation/#dfn-acquire-a-position
void Geolocation::acquire_a_position(GC::Ref<WebIDL::CallbackType> success_callback,
    GC::Ptr<WebIDL::CallbackType> error_callback, PositionOptions options, Optional<WebIDL::UnsignedLong> watch_id)
{
    // 1. If watchId was passed and this's [[watchIDs]] does not contain watchId, terminate this algorithm.
    if (watch_id.has_value() && !m_watch_ids.contains(watch_id.value()))
        return;

    // 2. Let acquisitionTime be a new EpochTimeStamp that represents now.
    HighResolutionTime::EpochTimeStamp const acquisition_time = AK::UnixDateTime::now().milliseconds_since_epoch();

    // 3. Let timeoutTime be the sum of acquisitionTime and options.timeout.
    [[maybe_unused]] HighResolutionTime::EpochTimeStamp const timeout_time = acquisition_time + options.timeout;

    // 4. Let cachedPosition be this's [[cachedPosition]].
    auto cached_position = m_cached_position;

    // FIXME: 5. Create an implementation-specific timeout task that elapses at timeoutTime, during which it tries to acquire
    //    the device's position by running the following steps:
    {
        // FIXME: 1. Let permission be get the current permission state of "geolocation".

        // FIXME: 2. If permission is "denied":
        if (false) {
            // FIXME: 1. Stop timeout.

            // FIXME: 2. Do the user or system denied permission failure case step.
        }

        // FIXME: 3. If permission is "granted":
        if (true) {
            // 1. Check if an emulated position should be used by running the following steps:
            {
                // 1. Let emulatedPositionData be get emulated position data passing this.
                auto emulated_position_data = get_emulated_position_data();

                // 2. If emulatedPositionData is not null:
                if (!emulated_position_data.has<Empty>()) {
                    // 1. If emulatedPositionData is a GeolocationPositionError:
                    if (emulated_position_data.has<GeolocationPositionError::ErrorCode>()) {
                        // 1. Call back with error passing errorCallback and emulatedPositionData.
                        // FIXME: We pass along the code instead of the entire error object. Spec issue:
                        //        https://github.com/w3c/geolocation/issues/186
                        call_back_with_error(error_callback, emulated_position_data.get<GeolocationPositionError::ErrorCode>());

                        // 2. Terminate this algorithm.
                        return;
                    }

                    // 2. Let position be a new GeolocationPosition passing emulatedPositionData, acquisitionTime and
                    //    options.enableHighAccuracy.
                    auto position = realm().create<GeolocationPosition>(realm(),
                        emulated_position_data.get<GC::Ref<GeolocationCoordinates>>(),
                        acquisition_time,
                        options.enable_high_accuracy);

                    // 3. Queue a task on the geolocation task source with a step that invokes successCallback with
                    //    « position » and "report".
                    HTML::queue_a_task(HTML::Task::Source::Geolocation, nullptr, nullptr, GC::create_function(heap(), [success_callback, position] {
                        (void)WebIDL::invoke_callback(success_callback, {}, WebIDL::ExceptionBehavior::Report, { { position } });
                    }));

                    // 4. Terminate this algorithm.
                    return;
                }
            }

            // 2. Let position be null.
            GC::Ptr<GeolocationPosition> position;

            // 3. If cachedPosition is not null, and options.maximumAge is greater than 0:
            if (cached_position && options.maximum_age > 0) {
                // 1. Let cacheTime be acquisitionTime minus the value of the options.maximumAge member.
                HighResolutionTime::EpochTimeStamp const cache_time = acquisition_time - options.maximum_age;

                // 2. If cachedPosition's timestamp's value is greater than cacheTime, and
                //    cachedPosition.[[isHighAccuracy]] equals options.enableHighAccuracy:
                if (cached_position->timestamp() > cache_time
                    && cached_position->is_high_accuracy() == options.enable_high_accuracy) {
                    // 1. Queue a task on the geolocation task source with a step that invokes successCallback with
                    //    « cachedPosition » and "report".
                    HTML::queue_a_task(HTML::Task::Source::Geolocation, nullptr, nullptr, GC::create_function(heap(), [success_callback, cached_position] {
                        (void)WebIDL::invoke_callback(success_callback, {}, WebIDL::ExceptionBehavior::Report, { { cached_position } });
                    }));

                    // 2. Terminate this algorithm.
                    return;
                }
            }

            // FIXME: 4. Otherwise, if position is not cachedPosition, try to acquire position data from the underlying system,
            //    optionally taking into consideration the value of options.enableHighAccuracy during acquisition.

            // FIXME: 5. If the timeout elapses during acquisition, or acquiring the device's position results in failure:
            if (false) {
                // FIXME: 1. Stop the timeout.

                // FIXME: 2. Go to dealing with failures.

                // 3. Terminate this algorithm.
                return;
            }

            // FIXME: 6. If acquiring the position data from the system succeeds:
            if (true) {
                // FIXME: 1. Let positionData be a map with the following name/value pairs based on the acquired position data:
                //    * longitude:
                //        A double that represents the longitude coordinates on the Earth's surface in degrees, using
                //        the [WGS84] coordinate system. Longitude measures how far east or west a point is from the
                //        Prime Meridian.
                //    * altitude:
                //        A double? that represents the altitude in meters above the [WGS84] ellipsoid, or null if not
                //        available. Altitude measures the height above sea level.
                //    * accuracy:
                //        A non-negative double that represents the accuracy value indicating the 95% confidence level
                //        in meters. Accuracy measures how close the measured coordinates are to the true position.
                //    * altitudeAccuracy:
                //        A non-negative double? that represents the altitude accuracy, or null if not available,
                //        indicating the 95% confidence level in meters. Altitude accuracy measures how close the
                //        measured altitude is to the true altitude.
                //    * speed:
                //        A non-negative double? that represents the speed in meters per second, or null if not
                //        available. Speed measures how fast the device is moving.
                //    * heading:
                //        A double? that represents the heading in degrees, or null if not available or the device is
                //        stationary. Heading measures the direction in which the device is moving relative to true
                //        north.
                GC::Ref<GeolocationCoordinates> position_data = realm().create<GeolocationCoordinates>(realm());

                // 2. Set position to a new GeolocationPosition passing positionData, acquisitionTime and
                //    options.enableHighAccuracy.
                position = realm().create<GeolocationPosition>(realm(), position_data, acquisition_time, options.enable_high_accuracy);

                // 3. Set this's [[cachedPosition]] to position.
                m_cached_position = *position;
            }

            // FIXME: 7. Stop the timeout.

            // 8. Queue a task on the geolocation task source with a step that invokes successCallback with « position »
            //    and "report".
            HTML::queue_a_task(HTML::Task::Source::Geolocation, nullptr, nullptr, GC::create_function(heap(), [success_callback, position] {
                (void)WebIDL::invoke_callback(success_callback, {}, WebIDL::ExceptionBehavior::Report, { { position } });
            }));
        }
    }
}

// https://w3c.github.io/geolocation/#dfn-call-back-with-error
void Geolocation::call_back_with_error(GC::Ptr<WebIDL::CallbackType> callback, GeolocationPositionError::ErrorCode code) const
{
    // 1. If callback is null, return.
    if (!callback)
        return;

    // 2. Let error be a newly created GeolocationPositionError instance whose code attribute is initialized to code.
    auto error = realm().create<GeolocationPositionError>(realm(), code);

    // 3. Queue a task on the geolocation task source with a step that invokes callback with « error » and "report".
    HTML::queue_a_task(HTML::Task::Source::Geolocation, nullptr, nullptr, GC::create_function(heap(), [callback, error] {
        (void)WebIDL::invoke_callback(*callback, {}, WebIDL::ExceptionBehavior::Report,
            { { error } });
    }));
}

// https://w3c.github.io/geolocation/#dfn-get-emulated-position-data
EmulatedPositionData Geolocation::get_emulated_position_data() const
{
    // 1. Let navigable be geolocation's relevant global object's associated Document's node navigable.
    auto navigable = as<HTML::Window>(HTML::relevant_global_object(*this)).navigable();

    // 2. If navigable is null, return null.
    if (!navigable)
        return Empty {};

    // 3. Let traversable be navigable’s top-level traversable.
    auto traversable = navigable->top_level_traversable();

    // 4. If traversable is null, return null.
    if (!traversable)
        return Empty {};

    // 5. Return traversable's associated emulated position data.
    return traversable->emulated_position_data();
}

// https://w3c.github.io/geolocation/#dfn-request-a-position
void Geolocation::request_a_position(GC::Ref<WebIDL::CallbackType> success_callback,
    GC::Ptr<WebIDL::CallbackType> error_callback, PositionOptions options, Optional<WebIDL::UnsignedLong> watch_id)
{
    // 1. Let watchIDs be geolocation's [[watchIDs]].

    // 2. Let document be the geolocation's relevant global object's associated Document.
    [[maybe_unused]] auto& document = as<HTML::Window>(HTML::relevant_global_object(*this)).associated_document();

    // FIXME: 3. If document is not allowed to use the "geolocation" feature:
    if (false) {
        // 1. If watchId was passed, remove watchId from watchIDs.
        if (watch_id.has_value())
            m_watch_ids.remove(watch_id.value());

        // 2. Call back with error passing errorCallback and PERMISSION_DENIED.
        call_back_with_error(error_callback, GeolocationPositionError::ErrorCode::PermissionDenied);

        // 3. Terminate this algorithm.
        return;
    }

    // 4. If geolocation's environment settings object is a non-secure context:
    if (is_non_secure_context(HTML::relevant_settings_object(*this))) {
        // 1. If watchId was passed, remove watchId from watchIDs.
        if (watch_id.has_value())
            m_watch_ids.remove(watch_id.value());

        // 2. Call back with error passing errorCallback and PERMISSION_DENIED.
        call_back_with_error(error_callback, GeolocationPositionError::ErrorCode::PermissionDenied);

        // 3. Terminate this algorithm.
        return;
    }

    // 5. If document's visibility state is "hidden", wait for the following page visibility change steps to run:
    run_in_parallel_when_document_is_visible(document, GC::create_function(heap(), [this, watch_id, success_callback, error_callback, options] {
        // 1. Assert: document's visibility state is "visible".
        // 2. Continue to the next steps below.
        // AD-HOC: This is implemented by run_in_parallel_when_document_is_visible().

        // FIXME: 6. Let descriptor be a new PermissionDescriptor whose name is "geolocation".

        // 7. In parallel:
        // AD-HOC: run_in_parallel_when_document_is_visible() already runs this in parallel.
        {
            // FIXME: 1. Set permission to request permission to use descriptor.

            // FIXME: 2. If permission is "denied", then:
            if (false) {
                // 1. If watchId was passed, remove watchId from watchIDs.
                if (watch_id.has_value())
                    m_watch_ids.remove(watch_id.value());

                // 2. Call back with error passing errorCallback and PERMISSION_DENIED.
                call_back_with_error(error_callback, GeolocationPositionError::ErrorCode::PermissionDenied);

                // 3. Terminate this algorithm.
                return;
            }

            // FIXME: 3. Wait to acquire a position passing successCallback, errorCallback, options, and watchId.
            acquire_a_position(success_callback, error_callback, options, watch_id);

            // 4. If watchId was not passed, terminate this algorithm.
            if (!watch_id.has_value())
                return;

            // FIXME: 5. While watchIDs contains watchId:
            {
                // FIXME: 1. Wait for a significant change of geographic position. What constitutes a significant change of
                //    geographic position is left to the implementation. User agents MAY impose a rate limit on how
                //    frequently position changes are reported. User agents MUST consider invoking set emulated position
                //    data as a significant change.

                // FIXME: 2. If document is not fully active or visibility state is not "visible", go back to the previous step
                //    and again wait for a significant change of geographic position.

                // FIXME: 3. Wait to acquire a position passing successCallback, errorCallback, options, and watchId.
            }
        }
    }));
}

void Geolocation::run_in_parallel_when_document_is_visible(DOM::Document& document, GC::Ref<GC::Function<void()>> callback)
{
    // Run callback in parallel if the document is already visible.
    if (document.visibility_state_value() == HTML::VisibilityState::Visible) {
        Platform::EventLoopPlugin::the().deferred_invoke(callback);
        return;
    }

    // Run the callback as soon as the document becomes visible. If we time out, do not run the callback at all.
    auto document_observer = realm().create<DOM::DocumentObserver>(realm(), document);
    auto timeout_timer = Platform::Timer::create_single_shot(heap(), VISIBILITY_STATE_TIMEOUT_MS, {});
    m_timeout_timers.append(timeout_timer);
    auto clear_observer_and_timer = [this, document_observer, timeout_timer] {
        document_observer->set_document_visibility_state_observer({});
        timeout_timer->stop();
        m_timeout_timers.remove_first_matching([&](auto timer) { return timer == timeout_timer; });
    };
    timeout_timer->on_timeout = GC::create_function(heap(), [clear_observer_and_timer] {
        dbgln("Geolocation: Waiting for visibility state update timed out");
        clear_observer_and_timer();
    });

    document_observer->set_document_visibility_state_observer([clear_observer_and_timer, callback](HTML::VisibilityState state) {
        if (state == HTML::VisibilityState::Visible) {
            clear_observer_and_timer();
            callback->function()();
        }
    });
    timeout_timer->start();
}

}